Pakistani authorities have made several arrests in connection with the bomb attack on a mosque in the northwestern city of Peshawar.

Deutsche Welle says Peshawar Police Chief Ijaz Khan told Reuters that several suspects had been arrested and police were investigating the possibility that they had received “internal assistance” to get inside the highly fortified compound where the mosque was located.

A senior official separately told AFP, on condition of anonymity, that police had detained 23 people in connection with the attack.  The official also confirmed that they were investigating possible help from the inside, adding that they were looking into possible connections with groups outside of Pakistan.

Mass media reports say at least 101 people, including 27 police official, were killed and 217 others injured on January 30 as a suicide bomber blew himself up inside a crowded mosque in Peshawar.

The attacker reportedly appeared to have passed through several barricades manned by security forces to get into the “Red Zone” compound that houses police and counter-terrorism offices in the northwestern city of Peshawar.

CNN reports that police suspect that 12 kilograms of explosives were used by a suicide bomber.  

The Associated Press (AP), citing the provincial police chief, reported on February 2 that the suicide bomber disguised himself in police uniform and did not raise suspicion among the guards. 

Police have reportedly identified the bomber are reportedly close to arresting suspects who helped him carry out the bombing, one of the deadliest ever in Peshawar.

According to AP, Pakistan’s defense and interior ministers in speeches to Parliament this week blamed the Pakistani Taliban, who maintain sanctuaries in neighboring Afghanistan, for orchestrating the bombing.

The Pakistani Taliban, known as Tehreek-e-Taliban (TTP), are a separate group but allied with the Afghan Taliban.

Peshawar is the capital of Khyber-Pakhtunkhwa province that borders Afghanistan and the site of frequent attacks by Tehreek-e Taliban.