Ten strangers entered the camera-filled house in east London on 14 July as part of an interactive TV experiment.
But as a precaution a telecommunications jammer is being fitted to the property so that no signals can be received in the area.
A phone call to a national newspaper had claimed stockbroker Nicholas Bateman - christened 'Nasty Nick' by viewers - managed to sneak in a tiny phone on the day they arrived.
Ten strangers entered the camera-filled house in east London on 14 July as part of an interactive TV experiment.
Each week one of them is evicted by phone vote, following secret nominations by their housemates, with the last surviving contestant scooping a £70,000 prize.
The Sun newspaper reported receiving a call from someone claiming to be an 'associate' of 32-year-old Nicholas.
The person suggested the city trader was receiving daily updates from a friend about what his fellow-contestants and Big Brother viewers thought about him.
'Concealed in wash bag'
He alleged Nicholas switches on the phone to vibrate alert at 0400 each day while lying underneath his covers and remains silent as the voice on the other end relays the latest news.
None of the housemates are supposed to have contact with the outside world and were all vigorously searched before they went in.
The phone was supposedly concealed in his washbag.
She said: "Following the allegations made in a national newspaper, the Big Brother production team brought forward one of the weekly security checks.
"It has found no evidence that a contestant has smuggled a mobile phone into the house."
Since Big Brother started, Nicholas has become the contestant viewers love to hate.
Lie over wife
Edited TV highlights and 24-hour internet coverage of developments in the Big Brother household have shown him playing his housemates off against each other.
Earlier this week, viewers saw him confessing that he had lied to his housemates by telling them his wife had been killed in a car crash to gain the sympathy vote.
The claim had been exposed as a lie in the papers days earlier.
But despite his unpopularity on the outside, Nicholas has yet to be nominated for one of the weekly evictions by any of his fellow contestants.