Purser Street house fire in London, Ont. on Nov. 21, 2020. (Jordyn Read/CTV London)

The city's major crimes unit is investigating the circumstances surrounding Saturday's fire in Northeast London that sent three people to hospital in critical condition.

Emergency crews were sent to a townhouse on Purser Street shortly after 11 a.m.

Two children and an adult were injured and rushed to hospital where they remain in critical condition.

The Office of the Ontario Fire Marshal has also been called to help with the investigation.

Police say more information will be released once it's available.

Witnesses are asked to contact police.