(CNN) Federal officials said Michigan and Flint leaders are not doing enough to comply with an emergency order on lead contamination in the city's drinking water .

In a letter Friday, the U.S. Environmental Protection Agency highlighted concerns to state and city officials. It said both sides should work hard to ensure they comply with the order issued last month.

EPA concerns included what it described as a shortage of qualified staff to help resolve the lead crisis. Under the emergency order, Flint was supposed to have "capable and qualified personnel" by February 5.

In addition to staffing, the federal agency said the city has failed to develop a comprehensive plan on anti-corrosion treatment of drinking water in Flint.

Both Flint city and Michigan state should have a plan to ensure the treatment plant consistently meets requirements, Mark Pollins of the U.S. Environmental Protection Agency wrote.

"Having a comprehensive and interactive plan, instead of individual pieces of a strategy, is essential to protect the residents of Flint," Pollins said.

City and state leaders have not submitted a plan for daily monitoring of water quality, he said.

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Michigan Department of Environmental Quality spokeswoman Melanie Brown said the agency was reviewing the letter and preparing a response.

"We look forward to continuing our collaborative work with the EPA to ensure that Flint water is safe to drink and that the proper regulatory support is in place," she said in a statement.

Flint spokeswoman Kristin Moore said via email that Mayor Karen Weaver "looks forward to working with the EPA and the state and federal governments to build the additional capacity needed for Flint to comply with all state and federal rules for safe drinking water."

Website more transparent

Despite the concerns, Pollins applauded Michigan for improving its website and making it easier to track development on the water crisis.

Hours before the letter, the research group that initially identified the contamination said the lead levels in the drinking water of Flint are "much, much, better."

New test results on lead in Flint water show much improvement compared with when the group measured the water back in August, Virginia Tech researcher Marc Edwards said Friday.

"At first glance they look bad, but they are not inconsistent with other cities that meet the federal lead and copper rule," Edwards told CNN in an email.

Nevertheless, Edwards cautioned, "people should keep using their lead filters and bottled water until further notice.

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"Everyone agrees that we should assume the water is unsafe," Edwards said.

Edwards is the lead researcher for the Flint Water Study, a research group that was first to publicly identify high levels of lead in the water last year.

Pipe replacement

Weaver said she wants the replacement of the city's lead pipes to begin next week so that the community can have clean water as soon as possible.

She urged Gov. Rick Snyder to pressure the state legislature to approve funding for the first phase of a $55 million lead pipe replacement plan.

The governor also favored speedy pipe replacement, but it's part of multistep process.