(Russia Today) Sweden’s largest Shiite mosque, which has thousands of members, has been badly damaged by a raging fire in the northern Stockholm suburb of JakobsFerg, in what police suspect was an arson attack.

The fire at the Imam Ali Islamic Center appears to have started in the building’s facade Monday overnight. The blaze was first reported shortly after 11pm on Sunday. Police suspect it was set intentionally. Swedish intelligence agency Sapo was immediately informed, as is routine when a mosque is involved.

“Apparently, it [fire] started from the outside,” Lars Bystrom, a press spokesman for the Stockholm Police, said, as cited by the Swedish daily Aftenposten.

“The scene of the fire has been sealed off in anticipation of forensic tests,” a police statement said, as cited by Reuters.

“It’s a very powerful fire,” Emil Skoglund of Storstockholm’s (Greater Stockholm’s) Fire Department said, Aftonbladet reported. More than 10 units from Storstockholm’s rescue service were deployed to fight the blaze, the newspaper said.

“It had burned through the ceiling before we arrived, so it was a rather heavy fire,” Tobias Akesson from Storstockholm told SVT.

It took firefighters over an hour and a half to extinguish the blaze outside the building.

Swedish police have detained a man on suspicion of being linked to the possible arson, a police statement said, according to Reuters. The suspect has not been identified and no further information is currently available.

A mosque spokesman said members of the community were “terrified.”

“We are very disappointed. This is the largest Shia mosque in Sweden, with thousands of members, and there are already a dozen members who have arrived here on the spot. They are very worried. I feel terrified, stressed and sad,” Akil Zahiri told SVT.

Zahiri said there were at least four people in the mosque when the fire was first noticed. A party had been held earlier in the evening, and another one was due to take place on Monday.

“It’s a very large building, the entire property is 3,500 square meters, so it’s hard to detect when something is burning,” Zahiri said.

According to preliminary estimates, “about 30-50 percent of the entire building has been damaged by the fire” he added.

In November last year, unidentified hooligans made their way into a mosque in the Bredang district of Stockholm, throwing fire crackers and painting swastikas and anti-Muslim slogans on the walls.

“One or more”perpetrators painted a swastika and wrote “kill Muslims” on the walls before fleeing the scene, SVT reported.

Sweden has seen a rise in attacks on mosques and refugee centers since the country took in a record 245,000 refugees in 2014 and 2015.

Since Sweden accepted so many asylum seekers in the fall of 2015, the EU has given the country a one-year break from resettling refugees. The pause will end this year, however, and from June to September some 3,766 people are to be transferred to Sweden, the country’s Migration Agency reports.