A bus carrying Moroccan workers crashed into a pillar under a highway overpass in France's Loire Valley early Friday, killing seven people and injuring 25, regional authorities said.

The bus was carrying 32 people from the southern Moroccan town of Tiznit to the Paris region when it crashed near the small town of Suevres, about 90 miles southwest of the capital, said Jean-Francois Moniotte, an aide to the regional administration chief.

The bus was left crunched against the pillar supporting the overpass. Clothing, a water bottle and crushed fruit lay strewn on the A10 highway, a major artery leading southwest of the French capital. Yellow curtains billowed out from shattered windows as rescue workers retrieved passports and other material.

Moniotte said no other vehicles were involved in the overnight accident. The circumstances of the crash remained unclear. One of the two drivers on the bus was among those killed

The central administration for the surrounding Loir-et-Cher region said the death toll had climbed to seven after one more person died Friday morning. The other 25 people aboard the bus suffered injuries, and three were in critical condition.

All the dead were adults, Moniotte said.

"It looks like a loss of control. Is this linked to a mechanical problem, drowsiness or a totally different cause?" junior minister for transportation, Dominique Bussereau, said on LCI television from the accident site.

He said there would be two investigations, one by the regional prosecutor and one by his ministry's accident investigation bureau.

The A10 highway was closed off and about 140 emergency workers were dispatched to the scene.

The French Interior Ministry put in place a rarely used emergency plan in the region to ensure quick and uninterrupted medical care for the victims.