CTV News Ottawa has learned there was a critical shortage of ambulances available to respond to emergency calls in the city of Ottawa Tuesday night.

The Ottawa Paramedic Service was at something called "Level Zero" for an undisclosed amount of time, requiring assistance from other jurisdictions.

This came just hours after the city said contingency plans were no longer needed to maintain services following a major COVID-19 outbreak within the paramedic service.

In a statement, the city confirmed the "Level Zero" status and said offload delays in emergency rooms remains a significant challenge.

"Our service is often impacted when paramedics are held in the emergency department for an extended time. Offload delays at hospital emergency rooms remain a significant challenge. This issue continues to affect Council-approved and legislated response times, now and in the future," said Kim Ayotte, the city's manager of emergency and protective services.

Fifty-three members of the Ottawa Paramedic Service, including paramedics and support staff, have tested positive for COVID-19 following an off-duty event at a restaurant earlier this month and more than 130 close contacts were identified. Paramedic chief Pierre Poirier said in a memo Tuesday that 61 service members had cleared COVID-19 protocols and returned to work adding, "contingencies are no longer required to mitigate service delivery impacts related to this incident."

Poirier had said in previous memos and statements that there were "minimal impacts" to service delivery in the city.

Ayotte echoed Poirier's statement that contingency measures were no longer required, and explained that during "Level Zero" events, the paramedic service is assisted by other emergency responders.

"On occasions where Level Zero is reached, the Service mitigates the impact as required with the support of Ottawa Fire Services and local paramedic services," Ayotte said.

"The City of Ottawa has always strived to maintain established response times for emergencies despite an increasing demand for service. To meet the demand for service, we have been hiring more staff, improving our deployment, conducting community paramedic home visits, and diverting patients away from emergency rooms," he added.