A 15-year-old boy has been arrested after suspected explosive substances were found at a house.
Army bomb disposal experts were called to the terraced council property in Hull along with scores of police, firefighters and paramedics following a tip-off.
A number of families were moved out of their homes as a precaution.
The teenager was arrested in the early hours of yesterday morning along with a 49-year-old woman and a 56-year-old man.
A Humberside Police spokesman said last night: "Agencies recovered substances from an address on Kilnsea Grove this afternoon, which were taken to a site in Hull to be disposed of safely.
"The substances have been made safe and seized as evidence. No one was injured."
The spokesman said police were called to Kilnsea Grove in the east of the city at 2.49am yesterday.
A number of police and fire service vehicles were still parked outside the house last night and officers had erected a blue forensics tent on the road in front of the property.
Police said most people in Kilnsea Grove returned to their houses yesterday evening.
Earlier, dozens of people living in the area gathered behind the police cordon to watch the soldiers go into the property.
One man said: "I can't believe what descended on us. There's army, police, ambulances, four-wheel drive ambulances, fire engines. Everything's here.
"They came in the middle of the night after a tip-off about stuff in the house. Then all hell broke loose. I've not seen anything like it."
Another Kilnsea Grove resident said: "They've just said they've found explosives inside and we're to stay well away.
"They've got everyone out just in case. You can't be too careful."
The spokesman said the Army's Explosives Ordnance Disposal Unit had been deployed as part of a multi-agency response.
Detective Inspector Jason Gourley said: "W e have arrested three people who are currently assisting us with our enquiries in connection with substances believed to be at a property on Kilnsea Grove.
"We appreciate that many people of Kilnsea Grove would have been inconvenienced when they were asked to evacuate their homes, so we would like to thank them for their patience, whilst we conducted inquiries and made the area safe for them to return.
"The evacuation was necessary in order to ensure every local resident was safe during the investigation, which was our top priority.
"I would like to reassure members of the public that we believe this is an isolated incident and we don't believe this incident is connected to any terrorist organisations."