Arson investigators are examining a fire at an Islamic centre that has put many in Houston’s Muslim community further on edge in the wake of this week’s killings of three Muslims in North Carolina.

Firefighters were called to a blaze at the Quba Islamic Institute in south-east Houston at around 5.30am on Friday, 45 minutes before morning prayers were scheduled to begin. No one was injured and the flames were extinguished in less than an hour, but one of three buildings was destroyed.

A Houston Fire Department spokesman told the Guardian on Saturday that the cause of the incident had not yet been officially released. Ahsan Zahid, son of the mosque’s imam, said that he was told the fire was started deliberately.

“When we spoke to the investigator he told us that it was an incendiary fire, which means that it was a suspected arson, that someone intentionally set the place aflame,” Zahid said in a video message on the institute’s Facebook page.

“And when we asked if it could have been any type of accident they said that it was not an accident, it was no type of electrical fault or any fault of our own, but that it was started by a person.

Zahid said the building housed materials that were going to be used for a renovation project, including computers. Zahid Abdullah, the imam, told the Guardian the building was not insured and that replacing it and its contents could cost in excess of $300,000. He said morning prayers at the mosque were usually attended by 100 to 200 people on Fridays.

Ruth Nasrullah, communications co-ordinator for the Houston chapter of the Council on American-Islamic Relations-Texas, was at a nearby mosque on Friday night. She told the Guardian two arson investigators visited to ensure that worshippers “felt safe and that they had safety precautions in place ... They did tell me that it was definitely on purpose, so it was arson, gasoline was used as the accelerant.”

Ahsan Zahid told Reuters that earlier in the week a man with his face covered was seen behaving suspiciously on the premises, and on Thursday someone drove by the centre and shouted mocking phrases in Arabic.

“We were leaving the premises, and a person driving a pickup truck was chanting in Arabic phrases, like terrorists do before they explode suicide bombs,” he said.

Three Muslim students were shot dead in Chapel Hill, North Carolina, on Tuesday night what some suspect may be a hate crime, adding to fears that recent high-profile murders of Westerners in the Middle East by Islamic militants are increasing tensions.

“There’s really rising anti-Muslim sentiment in this country that we see manifested in a number of ways,” Nasrullah said. “We’re always on a heightened sense of alert, we’re aware that there could potentially be danger to ourselves or to the mosques. It varies however according to the different locations.”

“Of course everyone is concerned, that’s the sort of thing, it was such a drastic incident, that it would naturally increase everyone’s sense of concern and wanting to be more vigilant with safety procedures. It definitely had an impact.”

Abdullah said the Quba institute is now planning to upgrade its security, including the installation of cameras.

Houston is the fourth-biggest city in the US and the most racially and ethnically diverse large metropolitan area in the country, according to an analysis of census data. An estimated 1.2% of Houston’s population is Muslim, double the national average.

But another Houston mosque was a target for arsonists in 2011, while in 2006, residents in one suburb mobilised against a plan to build a mosque, claiming that it could become a breeding ground for terrorists and prompting a local farmer to hold pig races on Fridays, a holy day for Muslims.

A gathering in Austin on 29 January for Texas Muslim Capitol Day was disrupted by protesters who shouted insults including “Go home”, “remember 9/11” and “Isis will gladly take you”.

Molly White, a Republican state representative for Belton, in central Texas, provoked controversy when she posted on her Facebook page that morning that she “did leave an Israeli flag on the reception desk in my office with instructions to staff to ask representatives from the Muslim community to renounce Islamic terrorist groups and publicly announce allegiance to America and our laws. We will see how long they stay in my office.”

Abdullah said he was encouraged by the support and sympathy offered to the institute from people in Houston and beyond following the fire, and that he would respond with compassion.

“If you know Muslims, we trust God,” he said. “If some crazy guy has done it, I still make prayer for him.”