The Northstar commuter train chugged into Target Field Station from Big Lake on Thursday morning a tad early, and a group of about 20 passengers stepped off clutching signs, petitions and letters. Their ultimate destination was the State Capitol, part of a plan to persuade legislators to extend the train line to St. Cloud.

“It’s important for St. Cloud to be linked to Minneapolis and the rest of the state,” said the Rev. James Alberts, chairman of GRIP/ISAIAH, a faith-based social justice group, and pastor of the Higher Ground Church of God in Christ of St. Cloud.

Northstar was originally planned to serve St. Cloud. But when the commuter rail began service in 2009, the final stop ended up in the much smaller city of Big Lake because of a lack of federal money. Buses now provide limited service between Big Lake and St. Cloud, and for some, that system works just fine.

But activists from GRIP/ISAIAH, and some legislators, including Rep. Jim Knoblach, R-St. Cloud, say it’s time to finish off the line. They note that the BNSF Railway recently added about 10 miles of double track between Big Lake and Becker, making expansion easier.

Yet estimates on how much it would cost to fund the missing link vary, and where the money would come from is unclear.

A 2010 Northstar Corridor Development Authority (NCDA) study concluded that the extension would cost $150 million. Last week, the Metropolitan Council said preliminary capital costs for building out the line would be about $40 million to $50 million. That does not include the cost of acquiring the right of way from BNSF, which would be negotiated.

“We’re open to it. We just have to figure out how to do it,” said Adam Duininck, chairman of the Met Council.

When asked to quantify possible right-of-way costs, BNSF spokeswoman Amy McBeth declined to speculate, saying the railroad would have to take into consideration how a Northstar expansion would affect current and future freight capacity. (Northstar shares track with BNSF freight trains.)

Advocates say federal funding for the build-out is unlikely, even though the federal government paid $162 million of the line’s original $320 million cost.

“Competition for federal funds is intense. Our chances of getting federal money are really pretty low,” said Leigh Lenzmeier, chairman of the NCDA and a Stearns County commissioner. The Federal Transit Administration, a key funder of such projects, looks at ridership numbers to justify investment, he said.

Ridership on Northstar was 722,637 last year, up just 1,423 riders over 2014 — an average of 2,548 passengers a day. With the exception of 2013, which was plagued with service issues, Northstar’s annual revenue has remained at about $16.5 million since 2010. Revenue from passenger fares is largely flat, about $2.3 million a year. As a result, Northstar is heavily subsidized by taxes — the subsidy per passenger was $13.73 in 2014.

Still, transit activists argue that Northstar suffers from a chicken-and-egg syndrome. They say the number of passengers lags because the line doesn’t reach St. Cloud — home to St. Cloud State University, St. Cloud Technical & Community College and the St. Cloud VA Health Care System, which would likely draw potential users. Immigrants and young people often prefer transit over driving — if they even have a car, said GRIP/ISAIAH organizer Anne Buckvold.

“How do you get ridership numbers up when the train stops in Big Lake?” she said, noting that the extension could ultimately end at the existing Amtrak station in St. Cloud.

“That’s the ‘If you build it, they will come’ approach,” said John Menter, executive director of the NCDA. “But Northstar hasn’t yet met expectations on what’s already been constructed.”

Meanwhile, officials from Stearns and Sherburne counties are slated to meet later this month to discuss a locally funded alternative to expand bus service between Big Lake and St. Cloud — maybe even bus rapid transit, Lenzmeier said. He estimates that new buses could be purchased for around $3 million.

Currently, five weekday Northstar Link bus routes serve the five Northstar commuter trains that arrive in the morning and afternoon rush hours at Big Lake, which is also served by a park-and-ride facility. Limited service on both the bus and train is available on weekends, too.

“It’s not like you’re putting people on broken-down school buses,” said Annette Meeks, founder and CEO of the Freedom Foundation of Minnesota and an opponent of expanding the line. “If people in St. Cloud need to, they can connect to the Cities.”