A Victorian jail is in lockdown, with authorities on site following an explosion.

The “small bang” went off at Barwon Prison near Geelong on Friday while prison officers conducted a routine intelligence search, Corrections Victoria says.

The area was evacuated and police and paramedics arrived but there were no serious injuries.

The jail was locked down an hour earlier than usual for the day, while emergency authorities were on site, a Corrections Victoria spokesman said.

He said officers were conducting a routine intelligence search when the small explosion went off.

“There was no physical damage and no injuries but police, fire and ambulance services have been notified and are attending,” he said.

“It’s being treated as an isolated incident.”

Police said they were investigating the blast.