In a joint operation, the anti-terrorism squad (ATS) and the Beed police on Sunday evening arrested Munjappa Giri, 34, in connection with the radio set explosion.
ATS chief Rakesh Maria told HT that with the arrest, the terror angle to the blast had been ruled out.
ATS officers said Giri had political as well as land rivalry with Gopi Tarkase of Kendrewadi in Beed.
The two had lodged police complaints against each other under the Atrocities Act and IPC sections pertaining to molestation.
Giri had allegedly thought of fixing Tarkase in sandalwood theft and ganja (marijuana) possession cases. But he could not arrange those things to plant on him.
After this Giri, who repairs transistors, thought he would get Tarkase framed in a blast case, said an officer, requesting anonymity.
According to sources, Giri bought the detonator for Rs50 and a telephone on August 21 from Kendrewadi. Police found the sale receipt of the telephone, which was in the name of Tarkase, which was planted in the bus by Giri.
Om Nimbalkar, 35, a bus conductor, had taken home a radio set found on a Mumbai-Ambejogai state transport bus on Friday. When he tried to replace the battery pack, it exploded.
Nimbalkar, his wife Usha, 30, mother Kusum, 53, and two-year-son old Kunal were seriously injured in the explosion.
The case was registered against unidentified persons under sections 336 (act endangering life or personal safety of others), 337 and 338 of IPC and Explosives Act.