A Plymouth hospital has made "significant improvements" to patient safety during surgery, the Care Qualify Commission (CQC) has found.
Concerns were raised about Derriford Hospital after four incidents in which swabs were left inside patients.
CQC inspectors made an unannounced visit to the hospital's operating theatres earlier this week.
The hospital said staff had worked "extremely hard" to make improvements to ensure the safety of patients.
The CQC had warned Plymouth Hospital NHS Trust it could face prosecution after an inspection in February found it was failing to meet three "essential" safety standards.
The inspection followed concerns raised after six serious incidents - referred to as "never events" because they should never happen - at the hospital within six months.
These included four swabs being left inside patients.
The CQC report into the February inspection, published earlier, found the trust was in breach of three essential standards.
These included patients being at an increased risk because important safety check-lists were not always being used effectively in some operating theatres.
It also found working practises in some theatres "did not promote an environment where clinical excellence could flourish" and that some patients receiving surgery were at an "increased risk" of unsafe care.
On 28 March, the inspectors returned to the hospital to check improvements had been made.
Bernadette Hanney, acting regional director of CQC in the South West, said that there had been a significant improvement to patient safety.
She said: "On our first inspection, it was a matter of some concern that even after the series of never events at Derriford - and despite the presence of our inspectors - the recognised surgical safety checks were not being carried out properly within some operating theatres.
"Our inspection this week has shown a real improvement.
"The trust has told us the surgical safety list is more detailed and is now a mandatory part of the process.
"Inspectors found clinical staff appeared to be more aware of the need to avoid serious preventable incidents.
"We are satisfied that Derriford Hospital has now taken this lesson to heart."
Dr Alex Mayor, medical director for Plymouth Hospitals NHS Trust, said: "It was not acceptable that some of our theatres were found to not be fully compliant with safety checklists.
"In the six weeks from their first visit, a significant amount of work has been undertaken within theatres.
"We are determined to maintain the momentum we have gained so far on improving patient safety in theatres and will continue to drive this forward."