CHESTER, England. (WTVO) — A British nurse has been charged with killing 7 babies and attempting to kill 10 more, according to news reports.

Lucy Letby, 32, a former nurse at the Countess of Chester Hospital, is on trial this week for the murder of five boys and two girls, according to the BBC.

Prosecutors allege that Letby used various methods, including insulin poisoning and injecting air into the bloodstream, while she was working in the hospital’s neonatal unit.

Authorities also said that Letby tried to kill some of the infants more than once before she succeeded.

The attacks were carried out between June 2015 and June 2016.

The hospital became alarmed after a sudden increase in infant mortality in the neonatal unit, which medics reportedly could not account for.

Prosecutor Nick Johnson KC told jurors, “Having searched for a cause, which they were unable to find, the consultants noticed that the inexplicable collapses and deaths did have one common denominator: the presence of one of the neonatal nurses and that nurse was Lucy Letby.”

Authorities conducted a “painstaking” review of the deaths, which eventually determined that the children had been deliberately given injections of insulin, causing their blood sugar levels to plummet.

The medical collapse of the 17 children was not “naturally-occurring,” Johnson said in court.

Initially, the hospital’s medical staff sought to uncover a natural occurrence, but “what the medical staff did not realize,” Johnson said, was that the deaths were “the result of someone poisoning them with insulin.”

One child was killed by air injected into their bloodstream, causing an air embolus.

Johnson also showed the court a chart detailing which nurses were on duty when the deaths occurred.

“If you look at the table overall the picture is, we say, self-evidently obvious. It’s a process of elimination,” he explained.

“Sometimes a baby that she succeeded in killing she did not manage to kill the first time she tried, or even the second time, and in one case even the third time.”

Letby has denied all the charges.