Families were evacuated from their Kenton homes for six hours last night while police dealt with a hazardous chemicals alert.

People in four houses surrounding a property in Chapman Crescent were told to leave their homes immediately as officers in chemical protection suits stormed the house and sealed off the road from 4.30pm until around 10.30pm.

Officers had been called to the house to reports of a domestic incident, but neighbours said they quickly evacuated the family inside when they found what police described as a “substance that needed to be examined”.

One neighbour, who asked not to be named, told the Harrow Times how he was denied access to his medication and had to sit in his car while officers worked at the scene.

And another neighbour described how residents could not get access to the street for hours.

She said: “We came home at about 7pm and we couldn’t get into Chapman Crescent, because they had blocked it completely.

“It was very dramatic – there was an ambulance there and we didn’t know what was going on, but they were there for hours.”

A man, in his 20s, was arrested on suspicion of handling stolen goods and a woman, also in her 20s, was arrested on suspicion of possession of Class A drugs.

After examining the substance found in the house, police declared it as non-hazardous, and denied it had any link to the ongoing incident in nearby Kenmore Road.

Forensic teams have been working at a house in the street for two weeks, after finding ammunition and hazardous chemicals in the home of Simon Marshall, 36, who was found dead there on June 16.

Chapman Crescent, a leafy suburban road, has seen its fair share of drama in recent years, with Tamil gang member and resident Arulmurugan Sepamalai, 22, jailed for his part in a violent turf battle in Wembley in May 2010.

And a cannabis factory was discovered by police in a house on the street in April 2009 after neighbours alerted them to burglars who had left the front door wide open.