SACRAMENTO, Calif. — A half-dozen states with backlogs for Medicaid enrollees were facing a federal deadline Monday to create plans for getting those low-income residents enrolled in health coverage.

The federal Centers for Medicare & Medicaid Services sent letters dated June 27 to Alaska, California, Kansas, Michigan, Missouri and Tennessee asking those states to address gaps in their eligibility and enrollment systems that have delayed access to coverage for poor and disabled people.

The letters were sent months after the first national sign-up drive under President Barack Obama’s health reform law.

The letters stated that those states had 10 days to come up with a response plan, but health advocates say there is no clear deadline for actually clearing the backlog.

The federal government “will remain in close contact with states to monitor their progress to ensure that they are facilitating Medicaid enrollment for those individuals eligible,” agency spokeswoman Marilyn Jackson said in a statement.

California had the largest backlog of 900,000 people in its Medicaid program as of May, out of 1.9 million people who enrolled. The state Department of Health Care Services reported that the backlog has been reduced to 600,000 as of Monday.

“We’ve been proud of much of what California has done to implement health reform, but we’re fundamentally concerned about people who need care and can’t access it — people who are going without care, people who are getting medical bills even though they’re eligible for Medi-Cal — that’s all happening today,” said Elizabeth Landsberg, an advocate with the Western Center on Law and Poverty.

California’s information technology problems stem from communication gaps between the state and county welfare systems. Many counties have reported trouble accessing state information necessary to process applications for Medi-Cal, the state’s version of the Medicaid safety net program.

Norman Williams, a spokesman for the California Department of Health Care Services, said the volume of applications also contributed to the backlog.

The group Health Consumer Alliance sent a letter to California Gov. Jerry Brown earlier this month with a list of recommendations, such as granting presumptive eligibility to all applicants who have waited more than 45 days, the federal timeline for determining eligibility. The group has been hearing from people whose applications are stalled even though they need medical care.

Mark Mullin, 36, an unemployed printing pressman from Whittier, California, applied for health coverage in February and was told his Medi-Cal application was being reviewed. On July 5, he ended up in the emergency room after two days of excruciating pain and had an appendectomy.

He’s now anxious about getting a big hospital bill and hasn’t made a follow-up appointment to see a doctor.

“I’m stressed out; I’m a wreck,” said Mullin, who could only afford to fill one of his four prescriptions from the surgery. “I don’t know how I’m going to deal with it. I don’t have an income, and I can’t look for a job because I’m not well.”

His case remains in limbo. Health advocates say Medi-Cal should cover his hospital stay, prescriptions and follow-up visits, but he could be billed in the meantime.

Alaska submitted its mitigation plan Monday saying it will continue to work on a new eligibility system for workers to make Medicaid determinations. So did Kansas.

Angela Minicuci, a spokeswoman at the Michigan Department of Community Health, said the state is working with the federal government to address technology issues. She said Michigan has enrolled 323,000 residents into the Healthy Michigan Plan, exceeding its 322,000 target for the year.

“We will continue to work to ensure Michiganders have access to health care coverage needed to lead healthy, productive lives,” Minicuci said.

Missouri said its staff had completed 39,000 of the 51,600 applications that have come through the federally run marketplace since February. Joseph Parks, director of the Missouri Department of Social Services, said only 8 percent of those applicants have been found to be eligible.

“The current transfer standards would appear to give too many applicants a false expectation of coverage under Missouri’s Medicaid Program,” Parks wrote in his response Monday.

The states facing the federal deadline are a mix of those that opted to expand Medicaid under the Affordable Care Act and those that did not.

Obama’s health reform law led to the signup of about 8 million people in private health care coverage through the insurance exchanges, while an additional 3 million people enrolled in Medicaid, the state-federal program for the poor and low-income.

The federal government initially picks up the full tab for the Medicaid expansion, which was accepted by about half the states.