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(CNN) -- An apparent arson attack on a mosque near the Belgian capital killed the institution's imam and left another person injured, a police spokeswoman said Monday.
A suspect was in custody in the deadly fire, which occurred about 6:45 p.m. in Anderlecht, a suburb of Brussels, police spokeswoman Marie Verbeke said. No further details about the suspect were immediately available, and Anderlecht Mayor Gaetan Van Goidsenhoven told the Belgian broadcaster RTBF that no motive for the attack was known.
"One must remain extremely cautious when speculating on what happened," he said. "The situation is extremely serious as someone has been killed."
The 46-year-old imam is believed to have died of smoke inhalation, while the surviving victim was treated for the same thing, Verbeke said.
Van Goidsenhoven said a crowd gathered outside the mosque after the attack, but "things are quite calm."
"There are obviously lots of emotions, but no signs of violence," he said.
CNN's Alexander Felton contributed to this report.