Residents were told to stay indoors today after police, paramedics and firefighters were called to an “unknown substance” in Watford.

Fire engines and multiple Hertfordshire Police vehicles were seen in Courtlands Drive as officers closed the road from around 1.40pm due to a spilled liquid reacting in the garage of a vacant house.

A man became unwell while carrying out a home clearance at the property and was assessed by the East of England Ambulance service for minor injuries but not taken to hospital.

.Police, fire and ambulance services were called to the chemical spill this afternoon. (Image: Supplied)

The road reopened at around 3.30pm and the chemical is now believed to have been sulphuric acid, according to the Hertfordshire Fire and Rescue service.

They added it was a “small, contained incident” and there was not any wider risk to the public.

Courtlands Drive resident Anne was told to stay indoors for over an hour this afternoon and said: “It’s not usual for something like this to happen in this road.”

Police, fire and ambulance services were called to the chemical spill this afternoon.Police, fire and ambulance services were called to the chemical spill this afternoon. (Image: Supplied)

She explained the house had been vacant for around two years after the previous occupant died and a removal van had been seen in the road before the incident.

Photos show two fire engines and multiple firefighters at the scene as they worked to secure the area.