Nearly 400 escaped prisoners remain at large in Nigeria on Monday after unidentified gunmen stormed the Abolongo Prison in southwestern Nigeria’s Oyo state on Friday, killing two guards and releasing 837 inmates, Agence France-Presse (AFP) reported.

A spokesman for Abolongo Prison, Olanrewaju Anjorin, told AFP on October 25 he visited the facility on October 24 and learned that 391 of the prison’s recently escaped inmates “were still at large.”

Anjorin said 837 inmates escaped the prison on October 22, adding that Nigerian authorities had already recaptured 446 of the fugitives as of October 25.

Anjorin, officially a spokesman for Nigeria’s federal correctional service in Oyo state, confirmed the jailbreak at Abolongo Prison on October 23. In a statement to the press, he said, “837 inmates awaiting trial escaped from the Medium Security Custodial Centre in Abolongo area of the state following an attack by gunmen on the facility on Friday night [sic].”

“The invaders were said to have arrived the center heavily armed with sophisticated weapons and, after a fierce encounter with officers on guard, gained entrance into the yard using dynamite to blast the wall,” the spokesman detailed.

The office of Oyo State Gov. Taiwo Adisa issued a statement on October 24 revealing two of the prison’s security personnel died in the attack on October 22.

“[T]he governor commiserated with the families of the two slain security agents: a corporal of the Nigerian Army … and an Operative of the Oyo State Amotekun Corps,” Nigeria’s Vanguard newspaper reported Sunday.

A third security guard at Abolongo Prison was seriously injured during Friday’s jailbreak and remained in “critical condition” at a local hospital as of Sunday, according to Vanguard.

The October 22 attack in Oyo state marked Nigeria’s third mass jailbreak this year. Unidentified gunmen have reportedly perpetrated all three incidents using explosive devices to gain entry to the correctional facilities.

A group of armed men stormed a prison in central Kogi state on September 13, using rifles and explosives to overtake the facility and allow 266 inmates to escape. Five months earlier, on April 5, a “large number” of gunmen targeted a prison in southeastern Nigeria’s Imo state. The group used “sophisticated weapons” and explosives to “forcefully release” 1,844 of the prison’s inmates, the Comptroller-General of the Nigerian Correctional Service, John Mrabure, said in a statement.

Nigerian authorities have blamed the country’s recent spate of prison attacks on unidentified criminal gangs.

“Jihadist group Boko Haram, which launched an insurgency in northeast Nigeria in 2009, has frequently attacked prisons to free inmates,” AFP noted on Monday. Boko Haram is an Islamist terror group notorious for mass kidnappings of schoolchildren.