Authorities have declared that a Christmas Day fire that damaged a mosque in Houston, Texas, was intentional.

According to the Houston Fire Department, the fire that broke out at the Savoy Mosque at 2:45 p.m. was "incendiary" and ruled out accident or natural causes, NBC News reported.

The Bureau of Alcohol, Tobacco, Firearms and Explosives, which is also assisting in the investigation, said the fire was suspicious as it had multiple points of origin.

About 200 people were inside the mosque for prayers an hour before the fire started. It was put out by firefighters in just a few minutes. No one was hurt.

U.S. Rep. Sheila Jackson condemned the attack on the mosque. "Attacking a place of worship is a despicable act," she said. "I will continue to closely monitor the possible criminal investigation and the safety of the members of the mosque. Our faith in humanity will not be intimidated and we stand together against any form of violence towards the innocent."

M.J. Khan of the Islamic Society of Greater Houston said the fire damaged everything in the mosque except for a copy of the Quran.

Worshippers gathered for a daily prayer Saturday at a temporary space in the strip centre, according to KPRC2.

"This is a place of worship, we're not going to stop worshipping just because a fire breaks out," Khan said. The mosque will be rebuilt as soon as possible.

The Houston chapter of the Council on American-Islamic Relations called law enforcement authorities to investigate a possible bias motive for the fire.

"Because of the recent spike in hate incidents targeting mosques nationwide, we urge law enforcement authorities to investigate a possible bias motive for this fire," said CAIR-Houston Executive Director Mustafaa Carroll.