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Editor's Note: This is an update on our multipart series from our partners at Reuters.

The chairman of a U.S. House committee that oversees child abuse issues opened an inquiry Friday into whether the federal government is failing to enforce a law meant to protect thousands of babies born dependent on drugs each year.

The inquiry, launched by Rep. John Kline of Minnesota, comes in response to a Reuters investigation last month that identified 110 examples of children who were exposed to opioids while in the womb and later died preventable deaths after leaving the hospital.

No more than nine states comply with a 2003 law that calls on hospitals to alert social workers whenever a baby is born dependent on drugs, the news agency found.

Since the law was enacted, the number of newborns diagnosed with Neonatal Abstinence Syndrome has skyrocketed – from 4,991 cases in 2003 to 27,315 in 2013, federal data show. A Reuters analysis found that thousands of drug-dependant newborns are sent home each year without a referral to social service agencies, contrary to the intent of the federal law.

Watch the NBC Nightly News report on babies born addicted to drugs

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Those referrals are intended to help social workers develop a "plan of safe care" for the newborns and mothers. Although most states fail to comply with the provisions, Reuters found none has lost federal funding.

In a letter Friday, Kline told Health and Human Services Secretary Sylvia Burwell that he was "deeply concerned" that the agency may not be enforcing the law.

“A Reuters investigation released in December cast serious doubts over whether these basic requirements in federal law are being followed," wrote Kline, a Republican who chairs the House Education and the Workforce Committee. The letter was co-signed by Todd Rokita, an Indiana Republican, who chairs a subcommittee on early childhood education.

“The Reuters investigation reveals the shocking and deadly consequences when these vital federal and state child welfare policies are not properly implemented and enforced,” the lawmakers wrote.

"Even more troubling, according to the Reuters report, there are some states that have failed to put these policies in place altogether, yet not a single state is being denied … funds.”

Related: Addicted Newborns: 'That Baby Is In Serious Danger'

Kline and Rokita asked Health and Human Services officials to explain the review process for determining whether each state has created a safe-care plan for babies born drug-dependent, and to make clear the consequences for states that do not comply.

Agency officials did not immediately respond to the lawmakers’ letter.

The primary backer of a key provision in the 2003 law, former Representative James Greenwood, said he was “delighted” that Kline and Rokita took “this step to light a fire under” the Department of Health and Human Services.

“Precious little lives are at stake,” Greenwood said.

Related: Addicted Mom and Baby Enter the 'Canyon Into Hell'

Last month, top U.S. senators also called for action. Sen. Charles Schumer, a Democrat from New York, asked for an “emergency surge” of funds to help protect the newborns, and Sen. Robert Casey, a Democrat from Pennsylvania, sought oversight hearings. The senior Republican in the Senate, Majority Leader Mitch McConnell, said the series “brings to the forefront a problem” that he has urged the Obama Administration to address faster.

The Reuters investigation, “Helpless & Hooked,” can be found here. Kline and Rokita’s letter to the Health and Human Services secretary can be found here.