Falmouth fire officials are still investigating the cause of a Steamship Authority shuttle bus fire last Saturday at the Palmer avenue parking lot.

“It’s not suspicious, and they’re leaning toward a mechanical issue, but no specific cause found,” Falmouth deputy fire chief Timothy Smith said Wednesday.

No passengers were on board and no one was hurt in the fire, but the 39-passenger bus was a complete loss after it became fully engulfed in flames in the lower end of the Palmer lot. The incident occurred late Saturday morning at approximately 11:40 a.m.

About 15 other nearby vehicles were also damaged by fire.

In a news release after the incident, Steamship Authority spokesman Sean Driscoll said the bus was on its way from the Palmer lot to the Thomas Landers lot to pick up passengers, when a driver on another SSA shuttle bus saw smoke coming from the back of the bus and alerted his fellow driver.

The driver returned to the Palmer lot shortly before the bus erupted in flames.

In the release Mr. Driscoll said the boat line would contact the owners of the damaged vehicles to offer assistance.

The bus was two years old and one of 26 buses that shuttle passengers from SSA lots to the ferry terminal in Woods Hole.