An investigation is underway after a shed on a property south of Nanaimo burst into flames following reports of a loud explosion.

Firefighters in Cedar, about eight kilometres southeast of Nanaimo, arrived to find a fully involved fire in a pump house on Brightman Road Monday afternoon

The blaze began to spread into a surrounding hay field before crews got it under control.

There were no injuries reported, according to North Cedar Fire Department.

Crews were soaking the field to prevent further flare-ups.

The cause of the fire remains under investigation.