A pedestrian was critically injured on Thursday morning when a taxi cab struck her on Elgin Street near Somerset Street.

Paramedics said the woman in her 60s was standing on the sidewalk when the cab struck her just after 9 a.m. She was taken to hospital with critical injuries.

The woman was found in cardiac arrest at the scene but revived by paramedics.

"Paramedics started aggressive resuscitation with CPR and airway management and managed to restart her heart," said Marc-Antoine Deschamps with Ottawa Paramedics.

The driver of the cab, a man in his fifties, was being treated for a medical emergency - it's unclear whether it was suffered before the crash. He is now in serious condition in hospital. 

"It might have been a cardiac problem so paramedics ran a bunch of tests including an ECGs and vital signs to try and figure out exactly what the problem was," Deschamps added. 

A passenger in the taxi was treated for minor chest injuries caused by the seatbelt. He was treated on scene and sent to hospital as a precaution. 

Initial reports of other pedestrians being struck are false.

Elgin Street is closed between Somerset and Cooper streets as the Ottawa Police Collisions Investigations Unit works to piece together what happened. 

"There are always charges possible, but it is too early to say at this point," said Investigator Kevin Bradford. "But that is always something that is considered when we start going through causation ... we have been made aware that the driver might have suffered some kind of medical emergency."