Detainees would had been speaking to the media via cell phones have not been contactable since.
Labour corrections spokesman Kelvin Davis said he had not heard from the men since about 10am Tuesday.
He had received Facebook messages overnight from family members and contacts with fears about the situation, he said.
There were unconfirmed reports some of the rioters were being kept in cage-like rooms with no beds, he said.
One woman told Mr Davis: "I've heard that 40 detainees are in birdcage. No beds, squashed like cattle. Given a bottle of water and a box of cereal. Everyone very tired and weak and dehydrated," she said.
"Urinating in their water bottles because they can't get to the toilet in time, not enough staff to escort them. [There's] five cages like this one."
Another woman told Mr Davis her partner, who is a Kiwi detainee on Christmas Island, had managed to hold on to his phone.
She sent Mr Davis screenshots of a text conversation the pair had after guards had taken over last night.
"The message said: Wasn't sure if you have spoken to any of the boys who are over there since the police have gone in so I thought I would just show you a few texts from my partner this morning," Mr Davis said.
"She said "Are you ok?" and he said "No they cracked my head open...and I think my jaw is fractured."
Another two texts read: "I'm so angry I was laying down on the ground with my hands behind my back and yet I still got smashed...Handcuffed then thrown down the stairs then shotgun to the head."
Australian authorities said all detainees were accounted for after the detention centre takeover.
The Australian Department of Immigration and Border Protection said some detainees were being treated for injuries.
"Five detainees have presented with injuries or medical conditions and are the subject of assessment and appropriate treatment from IHMS medical professionals," the department said.
"None of the matters are life-threatening. It is not known whether these injuries were sustained during the disturbance itself or during the resolution of the operation."
Some force was used during the takeover and the detainees were now "secured" in undamaged areas of the centre, the department said.
"Some force was used with a core group of detainees who had built barricades and actively resisted attempts to secure compounds, including threatened use of weapons and improvised weapons."
There were reports of some detainees barricading themselves inside with petrol bombs, machetes and chainsaws after raiding a garden shed for weapons.
Two bus-loads of guard reinforcements were trucked to Christmas Island on Monday night and patrolled the perimeter of the centre as sirens sounded, before storming inside.
