Two Ottawa residents have been charged with arson relating to Friday's massive fire at a Richmond road plaza that caused about $5 million in damages and completely destroyed five businesses.

Wael Chamoun, 29, and Shyla McGregor, 21, appeared in court Saturday and were remanded into custody. Each suspect faces five charges.

Ottawa police and fire officials are working with the Fire Marshal's office on the forensic investigation.

They are also continuing to investigate a series of explosions at a Bank Street commercial building in Old Ottawa South late Thursday night.

Fire officials say the second floor of the two-storey building, which houses West Coast Video and Elee Spa, was fully engulfed in flames when crews arrived.

Arson has been confirmed as the cause.

Meanwhile, a person of interest was released from custody relating to a Friday fire at Oil Changers Automobile on St. Patrick Street.

Firefighters say the blaze began inside the building at about 1 a.m. and heavy smoke prevented them from entering.

A neighbouring Tim Horton's restaurant was damaged by flames, and a nearby house was evacuated as a precaution. Damage is estimated at $700,000.

Police say there is no evidence linking the three fires.

Meanwhile, a 22-year-old man found in a hotel remains in critical condition after sustaining severe burns. The cause remains under investigation.