On the first springlike weekday of the year, some downtown Minneapolis workers left the skyways and headed to the food trucks that have once again begun to line Marquette Avenue.

With lines on the street getting longer by noon, it was business as usual — though some of the people inside the trucks were thinking more about the risks of their increasingly popular business.

It’s still unclear what caused a food truck parked in Lakeville to explode late Friday, damaging houses and rattling residents. But there’s little doubt that food-truck season is beginning as the weather warms.

There are 130 to 140 food trucks in the state, with 90 of them active at a given time, according to the Minnesota Food Truck Association.

Each one is inspected when it’s initially licensed. All food trucks are inspected like restaurants for food safety issues at least once a year. Some face additional regulations that apply to commercial vehicles. But nobody is keeping a routine eye on food trucks’ propane tanks.

John C. Levy, president of the Minnesota Food Truck Association, confirmed Monday that there is no federal, state or municipal agency that routinely inspects a food truck as an entire entity for problems such as propane leaks or other vapors that could spark an explosion.

“There is nobody that specifically checks for [propane] leaks,” he said. “I think that can come across as rather reckless but in practice it isn’t because of the rarity of that happening and the fact that if there’s a leak of gas, you can smell it.”

Levy said he researched the issue and found a total of five explosions, including Lakeville and one in Philadelphia last summer that killed two people.

He said food-truck operators protect themselves by making sure the service provider that fills the tanks is properly licensed, knows what they’re doing and checks all valves. “Then we do our own checks periodically,” he said.

Regular inspections

Inside the handful of food trucks parked in downtown Minneapolis on Monday, the people wrapping up sandwiches and tossing baskets of fries over hot oil said they weren’t shaken by he Lakeville explosion.

Workers were confident that the small spaces where they serve up lunch were well maintained — and explosions were the kind of unlikely accidents that can happen in many industries.

But Rommy Ayoub, co-owner of the Flavor Wagon — a truck he said is one of a few in the area that doesn’t use propane gas — said the Lakeville incident got him thinking again about the risks that can come with the business.

“When I was shopping around for insurance and realized a lot of the big companies won’t cover [food trucks], I realized maybe something was going on,” he said.

Ayoub said his truck and others are inspected regularly, and sometimes randomly. He recalled that inspectors came out last year to deal with a nearby truck that was leaking water.

Which agency does the inspection depends on where a truck is licensed.

In Minneapolis, fire officials inspect some trucks and the city’s health department handles food safety checks. Licensing inspectors ensure that trucks have received all required inspections from outside agencies before granting them permission to operate in the city.

In St. Paul and many other cities and counties, the trucks are licensed by the Minnesota Department of Health. That license is renewed every year.

Trucks weighing a total of more than 10,000 pounds — including equipment, food and personnel — are considered commercial vehicles and are subject to state and federal regulations, administered by the state Department of Public Safety (DPS). Those regulations can include that propane tanks are properly secured and drivers have the proper documents, said Lt. Tiffani Nielson of the State Patrol.

Those inspections ensure that the vehicle is in good working order and that propane tanks are properly secured, but don’t check for leaks. There is no special category for food trucks and those under 10,000 pounds aren’t subject to DPS inspection.

Nielson said the commander of the DPS commercial vehicle division met with the Food Truck Association a year ago to provide information regarding commercial vehicle regulations.

Ongoing investigation

Food trucks are inspected at random at least once a year for food safety and sanitary procedures, said Doug Schultz, a spokesman for the Health Department.

Motley Crews Heavy Metal Grill, the truck that exploded in Lakeville, was inspected five times since it received its first license in 2012. The last was Aug. 8, 2014, at Lakefront Days in Prior Lake. No violations were found. Minor violations were found in previous inspections; one concerned a cook who was handling sandwiches without wearing gloves, another concerned a too-high concentration of cleaning solution.

The cause of Friday’s explosion is under investigation, said Lakeville Fire Chief Mike Meyer. “Unfortunately, it’s going to take some time because it’s not just us or the state fire marshal involved, it’s insurance companies as well,” Meyer said. “We all have to go through this together.”

Levy said the Minnesota Food Truck Association would be taking a another look at best practices, as it did when the Philadelphia explosion occurred. The group may recommend safety measures to food-truck operators.

Levy said the association is “open to working with any regulators interested in taking up the propane question. Our only hope is that it’s not another whole layer of regulation but an add-on to something that already occurs.”