Thai police have said a second suspect arrested in connection with last month’s deadly bombing at a Bangkok shrine was carrying a piece of paper with a chemical formula used to make explosives written on it.

Speaking Thursday, National Police spokesman Prawut Thavonsiri said they believe the formula is based on acetone, a volatile and flammable substance.

These mix of chemicals you can easily obtain anywhere legally, but when you combine them, they become a chemical that is quick to catch fire and can be developed to become a detonator

This formula can also be used to enlarge the radius of the bomb. It could be used for both of the bombings. But when the bomb detonates, this element (if used in the bomb) would disappear immediately because it’s an amplifier.

The same suspect’s fingerprints also matched those taken from possible bomb-making material found at an apartment in Bangkok at the weekend, police said Wednesday. He was apprehended on Tuesday trying to cross the border into Cambodia.

On Thursday, Thai military authorities identified him as Yusufu Meerailee and named the other suspect in custody as Adem Karadak. Police said the two men shared the apartment in the capital where Karadak was caught on Saturday.

Both men had been traveling on false documents, according to the authorities.