A professor has been killed, one person has been seriously injured and up to 20 people are missing after an explosion at a chemistry college in France.

Police and fire services said the blast occurred at 12.25pm (1125 GMT) on the campus of the Ecole Nationale Supérieure de Chimie de Mulhouse (ENSCMu), one of France's oldest scientific schools in the town of Mulhouse, near the border with Germany.

"We thought it was an earthquake," Jean-Pierre Langer, a local resident, told local television. "It really shook."

The explosion ripped through the ground floor of the college's chemistry faculty and started a fire. It was heard across town and rescuers had to fight their way through heavy smoke. The cause of the blast was not immediately known.

"One person died, one person was seriously injured, 15-20 were reported missing who could be under the rubble and around 150 people were involved in the explosion," Bertrand Ley, a local fire brigade captain, told LCI Television.

Witnesses said the fire burned in several places before being extinguished. Windows across the campus were shattered. Cedric Ridepi, a witness, told LCI that he had seen "the inside (of the building) devastated. There were several seats of fire. There were screams from inside. I saw one wounded person."

The death of the professor was confirmed by the local government for the Haut-Rhin region, where Mulhouse is located. Many of those who escaped the building were said to be in shock.

According to the website of the college, which was founded in 1822, it has 185 undergraduate students enrolled in a three-year course, 90 Phd students and a teaching staff of more than 50 academics. Of a total community of 650 people, 350 work directly in its laboratories. The school teaches a broad range organic and inorganic chemistry courses, including "safety measures in the chemical industry".

The UNEF student union said the complex was not occupied by students as part of protests against a youth jobs law that have hit other universities in France.

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