Inmates are reported to have taken over part of a prison wing. Officials at HMP Northumberland confirmed a "disturbance" was under way, but dismissed as "speculation" the suggestion of a stand-off between inmates and guards.
A spokesman for Sodexo, which operates the prison, said: "We can confirm there is a disturbance at HMP Northumberland.
"It is confined to part of one wing of the prison and we are working to resolve the situation as quickly as possible."
The incident has been ongoing since around 7.30pm. The Sodexo spokesman added: "It is not quite resolved yet."
Prison guards found a mobile phone hidden in a box of hollowed out Weetabix.
Several of the breakfast cereal biscuits had been cut through the middle leaving a hollow where the phone was stashed.
The phone and doctored cereal were then carefully repackaged before being sent to a prisoner.
Inmates are not allowed mobile phones in prison and must use public payphones.
Prison staff should receive specific training on how to support women, a report has suggested, after it was claimed women prisoners are "vulnerable to abuse".
Chris Sheffield, chair of the Commission on Sex in Prison, said:
Women in prison are particularly vulnerable and more likely than men to have a history of being a victim of violence or sexual abuse.
It is important that policies recognise these differences and are developed in order to protect the vulnerable.
It is equally important that staff in women's prisons receive specific training on working with women.
Women prisoners are "vulnerable" to abuse in prison with some coerced into sex with staff in return for favours such as cigarettes or alcohol, campaigners have warned.
The findings are published in the second briefing paper from the Commission on Sex in Prison, which was established by the Howard League.
The report suggests prison staff need training and guidance on how to support women, recognise bullying and identify relationships between prisoners.
With 81% behind bars for non-violent crimes, more support for female prisoners is needed, the new justice minister tells Daybreak.Read the full story ›
Government cuts could be behind half of convicted sex attackers, violent criminals and burglars avoiding prison sentences, Labour said.
Some of these crimes are so serious and violent that members of the public rightly expect them to lead to a prison sentence.
One of the concerns is that this is being done in order to save money. Justice done on the cheap like this risks prisoners reoffending rather than being reformed, which means more victims and misery.
This will be an insult to many victims of crime who want to see those who committed crimes against them properly punished and rehabilitated.
Ministers have been accused of insulting victims after it emerged that half of convicted sex attackers, violent criminals and burglars are avoiding prison sentences.
Thousands of serious criminals have walked free from court, including 46% of paedophiles who abused children aged under the age of 13.
Some 49% of those convicted of sexual assault in 2012 - 2,324 offenders - did not receive a custodial sentence, and nor did many burglars and drug dealers.
Shadow justice secretary Sadiq Khan, who used parliamentary questions to obtain the statistics, said Government cuts were undermining the system.
"This will be an insult to many victims of crime who want to see those who committed crimes against them properly punished and rehabilitated," he told the Daily Telegraph.
Since the European Court of Human Rights ruled that whole life terms were a breach of human rights, the Government has been looking at a range of options to deal with the issue.
They now think they may have come up with a way around the ruling, by allowing judges to hand out US-style long sentences, perhaps up to 100 years. They are due to present their proposals to the Court in Strasbourg later this month.
The ECHR is an institution with which the Government is quite happy to pick a fight, and this would give Tory backbenchers another reason to ask David Cameron to take a stronger line against the court and perhaps even threaten to pull out of the European Convention.
There are currently 49 criminals serving whole life terms in English prisons, and David Cameron has vowed to ensure that "life means life" for the worst offences.
Those serving full life terms include Jamie Reynolds, who pleaded guilty to the murder of Shropshire teenager Georgia Williams last year.
Mark Bridger, who was jailed for killing five-year-old April Jones, is also serving a whole life sentence.
David Cameron has promised to ensure murderers can be kept in jail for life amid suggestions that the Government could introduce 100-year-sentences.
The Prime Minister's comments follow a long-running confrontation with the European Court of Human Rights, which has declared life sentences in England illegal because they offer no "right to review".
Ministers believe they can sidestep the ruling by letting judges sentence for hundreds of years, the Telegraph has reported.