The executive director of Ottawa's Islam Care Centre said someone left a "hateful" note before setting a fire behind the building overnight.

The suspicious incident is the second in a week at 375 Somerset St. W. after a man vandalized that building, as well as the Ottawa Mosque.

Ottawa police say someone set a pile of debris on fire outside the Islam Care Centre in the early morning hours of Wednesday, April 19, 2017. (Mathieu Theriault/Radio-Canada)

Omar Mahfoudhi said he watched surveillance footage of the suspicious incident, which he said shows a man slip a piece of paper into the mail slot at the front door of the building around 2:10 a.m. Wednesday. Approximately five minutes later, the suspect set a pile of debris at the rear of the building on fire.

The flames blackened a door and wall, but didn't spread to the rest of the building.

While he has not seen the note, Mahfoudhi said responding officers described its tone to him.

"I do understand it was hateful in nature, but I don't know the content," Mahfoudhi told CBC News.

Police won't confirm note

Ottawa police say someone set a pile of debris on fire behind the Islam Care Centre at 375 Somerset St. W. in the early morning hours of Wednesday, April 19, 2017. (Mathieu Theriault/Radio-Canada)

The Ottawa Police Arson Unit is investigating the fire, but police spokesperson Const. Marc Soucy wouldn't say whether a note was left.

"We don't disclose evidence of our investigations," Soucy said. He did confirm officers seized items during the investigation.

No arrests have been made and police have not identified a suspect in Wednesday's incident.

On April 12, police said one suspect smashed a window at both the Islam Care Centre and the Ottawa Mosque on Northwestern Avenue.

Ottawa police said a 27-year-old man turned himself in the same day. During the arrest, he allegedly assaulted a police officer.

He is facing two charges of mischief and one count of assaulting a police officer