“There is an indication from [Cai’s] cellmate's initial statement that [Cai] had been [digging the tunnel] for about five to six months using several tools that we have confiscated,” Jakarta Police spokesperson Yusri Yunus told reporters on Tuesday.

According to the statement, the escapee allegedly took the tools for the construction of a prison kitchen and used them to dig the tunnel inside his cell.

Tangerang Police chief Sugeng Hariyanto previously said that the cellmate had refused Cai’s invitation to escape the prison with him.

Yusri said that the police had formed a team with the prison authorities to further investigate the case for the possible involvement of other parties.

The Law and Human Rights Ministry’s corrections directorate-general spokesperson, Rika Aprianti, said separately that the ministry would work together with the police to recapture the escaped prisoner.

She added that the corrections directorate general, along with the ministry’s inspectorate general and regional office in Banten, would question the penitentiary’s officers.

Tangerang Penitentiary warden Jumadi previously said that Cai, a Chinese national who also goes by the name of Cai Ji Fan, escaped the penitentiary on Monday at around 2:30 a.m. through a 30-meter long tunnel that he had dug and which was connected to a sewer outside the prison walls.

The convict was found guilty of drug trafficking and sentenced to death in 2017. He had been transferred to the penitentiary from the Pemuda Prison, also in Tangerang.