– The highway crash that injured the Timberwolves’ Karl-Anthony Towns on Thursday and led to the All-Star missing his first NBA game was caused when a semitrailer truck hit from behind the car he was riding in, authorities said Saturday.

Early Saturday evening, Wolves interim coach Ryan Saunders said Towns was still in the league’s concussion protocol and would miss Saturday’s game against the Milwaukee Bucks at Fiserv Arena.

Until Thursday, Towns had started 303 consecutive games in his four-year career. Now he has missed two straight.

The collision occurred about 1:30 p.m. in Minneapolis on southbound Interstate 35W near the 38th Street overpass as Towns was being driven to Minneapolis-St. Paul International Airport ahead of Friday’s road game vs. the New York Knicks, according to the State Patrol.

Wolves assistant strength coach Kurt Joseph, 29, was driving Towns to the airport when he slowed for traffic. That’s when the semi, driven by 51-year-old Michael Arndt of Janesville, Minn., hit the car from behind, according to the patrol.

Towns complained of a minor injury but declined medical attention at the scene, the patrol said. No other injuries were reported.

All vehicle occupants had on their seat belts, and alcohol is not considered a factor in the crash, which remains under investigation.

Despite their lone All-Star being put on the concussion protocol and out of the lineup Friday, the Wolves defeated the Knicks 115-104.

Saunders said Towns “took some steps to go through things,’’ but remained in the concussion protocol. Saunders was unable to provide a timetable for Towns’ expected return. “We’ll give further updates as we get them.’’

Saunders said Towns was unhappy at not being able to play. But it had more to do with him wanting to help the Wolves win and less about the sudden end to his run of consecutive starts.

“It’s definitely bothering him,’’ Saunders said. “It’s all about being there for his teammates, contributing. He had someone run out and get a sport coat (before Friday’s game in New York) so he would be dressed properly on the bench so he could be with his teammates.’’

Happy birthday

Saturday was Andrew Wiggins’ 24th birthday. It would also have been Flip Saunders’ 64th.

For Ryan Saunders, who still calls his dad his best friend, it’s a difficult time.

He said his mom was able to make the trip to Milwaukee, so they were able to have lunch together Saturday.

Back home, Ryan’s sisters and his wife and others assembled.

“They’re having a piece of cake — he loved cake — and they’re watching the game,’’ Ryan said. “So we still try to honor him.

“Obviously I wish he was here for his 64th birthday,’’ Saunders continued. “They can be hard days on the anniversaries. But we draw strength from that, too.’’

Etc.

• Meanwhile, Saunders was asked if he got Wiggins a present. “He doesn’t need a present from me,’’ he said. “Just a handshake.’’

– the Wolves have an open roster spot. Will they move quickly to fill it?

“We do have a roster spot open, and obviously there are names out there, but we’re just focused on [Saturday’s game],” Saunders said. “And we’ll reconvene and move forward with that roster spot [later].’’