Kano (Nigeria) (AFP) - Four people were killed when an improvised explosive device seized from Boko Haram Islamists detonated at a police station in northeast Nigeria, a rescue official said on Thursday.
"They were all police officers," the Adamawa state coordinator for the National Emergency Management Agency (NEMA), Sa'ad Bello, told AFP by telephone.
"Five or six" others sustained minor injuries and were treated in different hospitals but later discharged, he added.
The blast in the Jimeta area of the state capital, Yola, happened at 11:30 am (1030 GMT) and sparked fears of another attack by Boko Haram.
The Islamist insurgents have attacked the city before and have targeted police stations and government buildings across the northeast.
But Adamawa police spokesman Othman Abubakar said: "There was an accidental explosion in an armoury manned by our bomb squad".
He said the device "killed one officer and mildly injured others". He was not immediately available to comment on the higher death toll.
"Contrary to speculation, the explosion had nothing to do with any sabotage or attack. We have recovered lots of explosives from these troubled areas," Abubakar added.
"Usually we screen them and store them for safe-keeping. We don't know what happened. Possibly this wasn't screened properly."
Aliyu Maikano, an official with the Nigerian Red Cross, said the blast "wrought massive destruction on the building" and sparked a fire.
Security personnel kept rescue workers at a safe distance because of fears of further explosions, he added.
On November 17 last year, at least 34 people were killed and 80 others injured when an IED went off at a lorry park in the Jambutu area of the city.
At least 27 people were killed and 96 wounded in a blast at a Jambutu mosque on October 23.
Another home-made bomb left at a camp for people displaced by the conflict in Malkohi, just outside Yola, killed seven on September 11.
The insurgency has left at least 17,000 people dead since it began in 2009 but over the last year a sustained counter-insurgency has recaptured territory lost to the rebels.
The group has since reverted to attacks on "soft" civilian targets such as markets, bus stations and mosques using suicide bombers and IEDs.