The attacker mingled with worshippers at a mosque in the Unguwar Shuwa area of Mubi and blew himself up towards the end of the morning prayers.
At least 50 people were killed on Tuesday when a suicide bomber blew himself up at a mosque in northeast Nigeria, police said, in an attack blamed on Boko Haram militants.
The blast happened during early morning prayers at the Madina mosque in the Unguwar Shuwa area of Mubi, some 200 km (125 miles) by road from the Adamawa state capital, Yola.
"So far we have at least 50 dead from an attack at a mosque in Mubi," Adamawa state police spokesman Othman Abubakar said.
"Several people were injured. We don't have the figure now because they have been taken to several hospitals for treatment.
"It was a [suicide] bomber who mingled with worshippers. He entered the mosque along with other worshippers for the morning prayers.
"It was when the prayers were on that he set off his explosives."
TRT World spoke to journalist Anna Cunningham for more details.
Asked who was responsible, Abubakar said, "We all know the trend. We don't suspect anyone specifically but we know those behind such kind of attacks."
The attack bore all the hallmarks of Boko Haram, the militants whose insurgency has left at least 20,000 people dead and more than 2.6 million others homeless since 2009.
Haruna Furo, head of the Adamawa state emergency management agency, and Musa Hamad Bello, chairman of the Mubi north local government area, both confirmed the attack.
They gave lower death tolls but both said the number of those killed was likely to rise.
Another emergency services official described the blast as "devastating". He said only that there were "high casualties".
Roof blown off
Abubakar Sule, who lives near the mosque, said he had just returned home when he heard the blast.
"I was there when the rescue was on and 40 people died on the spot and several others were taken to hospital with severe and life-threatening injuries," he added.
"The roof was blown off. People near the mosque said the prayer was mid-way when the bomber, who was obviously in the congregation, detonated his explosives.
"This is obviously the work of Boko Haram."
In recent months, Boko Haram activity has been concentrated on the far north of Adamawa state, around Madagali, which is near the border with neighbouring Borno state.
Earlier this month, at least two civilians were killed when dozens of Boko Haram militants tried to storm the town of Gulak but were repelled by soldiers.
There have been repeated suicide bombings in the area, which lies not far from the Sambisa Forest area of Borno, where the militants had a base.
Boko Haram militants are also said to be hiding in the Mandara mountains, to the east of Adamawa state, which forms the border with neighbouring Cameroon.