Espinosa was arrested on October 5 and charged with illegal possession of dangerous drugs and firearms.
Police chief Jovie Espenido of the town of Albuera in the central Philippine island of Leyte said he saw the name of the high-profile senator in a logbook of transactions kept by Mayor Rolando Espinosa.
A senator's name is allegedly in a record book of drug transactions of an arrested town mayor with links to the drug trade, a police chief said Friday.
"May pangalan ng senador nga nakita ko - dating secretary ng DOJ [Department of Justice] siguro iyon," police chief Espenido said.
Espenido did not mention a name. In the Philippines' roster of sitting senators, only Leila De Lima has held the post of Justice Secretary under the previous administration of President Benigno Aquino III.
The police chief's statement comes after he filed on Wednesday a case of illegal possession of dangerous drugs against De Lima before the Ombudsman in the Tacloban City, the provincial capital of Leyte.
Mayor Espinosa has been tagged by President Rodrigo Duterte as one of the protectors of illegal drug activities.
His arrest followed a raid on his home on August 10 where illegal drugs, bomb-making ingredients, firearms, and the logbook were seized.
De Lima, who has been accused by inmates at the national penitentiary of having received money from illegal drugs to fund her senatorial bid, has denied links to the illegal drug trade.