On Thursday, 43 Congress MLAs left the party to join the People's Party of Arunachal Pradesh, according to NDTV.
The Indian Express had earlier reported that Chief Minister Pema Khandu, along with two-thirds of party MLAs would jump ship.
NDTV reported Pema Khandu saying, "Have met the Assembly speaker and informed him that they are merging the Congress with the People's Party of Arunachal or PPA."
In the 60-member House with an effective strength of 58, Congress had the support of 47 MLAs, including two Independents, while Opposition BJP has 11 members.
Khandu was sworn in as the ninth chief minister on 17 July after months of political turmoil in the state. In a dramatic turnaround in this land-locked state on 16 July, Congress replaced Nabam Tuki by choosing Khandu as the new Congress Legislature Party (CLP) leader, who staked claim to power on the basis of support of 45 party MLAs along with two Independents.
In fast-changing developments, Kalikho Pul, the late rebel-turned chief minister, who was unseated by the Supreme Court, returned to the party fold with 30 dissident MLAs.
Hours ahead of a scheduled floor test in the Assembly, which Tuki was directed by the governor to take, the Congress Legislature Party met and elected Pema, son of late chief minister Dorjee Khandu, as its new leader.
Tuki proposed the name of Khandu while Chowna Mein, sworn in as Deputy Chief Minister, seconded it, which was unanimously accepted by 44 MLAs who were present.
With inputs from PTI