For years, inmates have complained of sexual abuse on Rikers Island. Now, the numbers are backing them up.

The city's Department of Correction quietly posted a report on its website late last week. The details show there has been a sharp rise in the number of sexual harassment and abuse allegations in city jails. 

From 2016 to 2017, the number of allegations, including staff-on-inmate allegations and inmate-on-inmate allegations, has gone up almost 40 percent, climbing past 1,100 last year. The report claims "increased reporting" is to blame for the uptick.

The figures sparked alarm among advocates and officials. 

"I found that report to be deeply alarming, and I think we're going to have to take a deeper look at why the allegations are going up," said City Councilman Keith Powers of Manhattan.

"I think it confirms what we have known, which is, sexual abuse is a really big problem in the jails and they aren't solving it," said Caroline Hsu of the Legal Aid Society.

It's not just the allegation increase that's caused concern. The climbing number of cases has also led to a big backlog. It means about 90 percent of the allegations from 2016 are still under investigation, 97 percent of cases from last year. 

That's more than 1,850 allegations of sexual harassment or abuse still waiting a final outcome, maybe months or years after it's been made. 

After speaking to NY1, Powers, the head of the City Council's committee on criminal justice, may now hold a hearing on the issue. 

"I think we may have to. It's something we're concerned about," Powers said. "I am deeply concerned with seeing how many cases have not even been investigated yet and whether we are abdicating our duty to people to make sure they are safe and secure."

Meanwhile, the department says it is dedicated to investigating every claim of sexual harassment and abuse in city jails. They are now using a hotline for crisis counseling. A spokesman tells us they have tripled the number of investigators to look into these cases, from six to 19.  

The city is supposed to investigate these claims in 90 days. Clearly, it doesn't hit that target. The department tells us they hope to get more investigators and that that may bring down the backlog.