After a lengthy battle a fire at a vacant St. Thomas hotel is out, and investigators are treating the blaze as suspicious.

St. Thomas fire crews were called to the former Ramada Inn, Monday night around 11:30 p.m. It took firefighters until 6 a.m. Tuesday morning to extinguish the blaze.

The hotel has been empty for several years and no injuries are reported.

Damage to the structure is estimated at $500,000.

Fire investigators were expected to remain on scene most of Tuesday.

The Ontario Fire Marshal's Office has also been called in.