It's thought the attack could last several days.
Greenock Prison Praised In Report
Greenock prison has been given a positive report by inspectors, but they say there is still room for improvement.
The prison has been praised for its "excellent'' links with the local community and the preparations made for prisoners being released, as well as positive relationships between staff and prisoners.
It was also commended for the good range of healthcare services available for both men and women.
The inspection, carried out in May this year, shows a range of improvements at HMP Greenock following a more critical report in 2009.
Inspectors noted that achievement of qualifications has been "quite limited'' while library provision is poor and in need of review.
Meanwhile, there are still issues related to the age and condition of the building itself, including dampness, and the "poor'' condition of the separate cells, although these are rarely used.
The report also noted that accessing dentistry appears at times to be problematic and does not reflect provision within the community.
There is a lack of an overall strategy within NHS Greater Glasgow and Clyde to guide the provision of addictions services within HMP Greenock.
HM Chief Inspector of Prisons for Scotland David Strang said: "Overall, this is a good report for HMP Greenock.
"When the two new community integration units are built and operational, there will be greater scope for the prison to work constructively with the prisoners to improve their preparation for return to the community''.
Sturgeon says Trump is on the "wrong side" of the debate.
The boys were found inside the Sainsbury's store at 2am on Tuesday.
The incident, which happened at Ibrox station, was reported to British Transport Police before 8pm on Saturday.
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