The approval of ballot initiatives legalizing marijuana in Washington state and Colorado left officials searching for guidance from the federal government on Wednesday, with major questions over whether the states could become the first in the nation to permit recreational use of the drug.

The Justice Department said it was reviewing the initiatives but would not comment further on how it would respond. A spokeswoman for the Drug Enforcement Administration said that its enforcement of federal law, which bans production, possession and sale of marijuana, “remains unchanged.”

The ballot initiatives in Colorado and Washington state were a step beyond the measures that have legalized marijuana for medicinal purposes in the District and 17 states, including Massachusetts, which passed such an initiative Tuesday.

Colorado Amendment 64 allows individuals 21 and older to buy up to an ounce of marijuana at retail stores that are regulated. Washington’s Initiative 502 is similar and allows adults 21 and older to buy up to an ounce of dried marijuana, or small amounts of marijuana-infused products.

In the run-up to the vote on the measures Tuesday, the Justice Department was unusually muted about the possible conflicts between federal and state laws should the initiatives pass, even as former DEA officials called on Attorney General Eric H. Holder Jr. to publicly oppose them.

Colorado Gov. John Hickenlooper (D) on Wednesday signaled his awareness of those conflicts, cautioning voters that it would take time to deal with the implications of the initiative.

“The voters have spoken and we have to respect their will,” Hickenlooper said in a statement. “This will be a complicated process, but we intend to follow through. That said, federal law still says marijuana is an illegal drug, so don’t break out the Cheetos or gold fish too quickly.”

Hickenlooper’s office called the Justice Department on Wednesday to get guidance on how the state should proceed. Eric Brown, a spokesman for Hickenlooper, said that Holder is scheduled to speak directly to the governor Thursday or Friday.

Washington Gov. Chris Gregoire (D) also indicated that she is uncertain about whether there will be a showdown with the federal government.

“The voters have decided to decriminalize marijuana possession and tax its sale and we will follow the will of the people,” Gregoire said in a statement. “We are entering uncharted waters and many questions lie ahead as we work to implement this law. Because marijuana is still illegal at the federal level, we are unsure how the federal government will proceed.”

Gregoire said that the state’s Liquor Control Board will be responsible for establishing the licensing and inspection procedures for the new measure over the next year.

Colorado’s initiative will go into effect by Jan. 5, according to Brown. The state’s general assembly, which meets between January and May, must then pass legislation creating the regulatory framework for the new law. Under the measure, the state would begin accepting and processing license applications for sales by Oct. 1 and start issuing licenses by January 2014.

Possession of marijuana would be legal, although it would not be legal to use the drug publicly.

Supporters of the measures in both states argued that they would bring in hundreds of millions of dollars in tax revenue, with the funds being used for education, health care and other government services. They also said that the initiatives would give proponents a chance to show that decriminalization of marijuana could benefit the country’s war on drugs.

In Colorado, the measure was supported by more than 300 physicians in the state, including Bruce Madison, the former associate medical director of faculty at the University of Colorado School of Medicine, who said that current laws waste “hundreds of millions of dollars in a failed war on marijuana, by ruining thousands of lives by unnecessary arrest and incarceration, and by causing the deaths of hundreds of people killed in black-market criminal activities.”

Opponents of the measures in both states warned of a federal crackdown and unauthorized drug use by children. They also argued that the states could attract “drug tourists.”

A similar proposal legalizing marijuana use was on the ballot in Oregon but did not pass.

In September, nine former DEA administrators wrote a letter to Holder expressing their concerns about the initiatives. The attorney general did not respond.

“To continue to remain silent conveys to the American public and the global community a tacit acceptance of these dangerous initiatives,” wrote the former administrators, who oversaw the DEA under Democratic and Republican presidents from 1973 to 2007. “We urge you to take a public position on these initiatives as soon as possible.”

The Justice Department can file suit to try to block state laws that it deems to have violated federal statutes. It did so, for example, after Arizona passed a law in 2010 that the state said was aimed at cracking down on illegal immigrants but that the Obama administration believed was unconstitutional.

On Wednesday, Justice Department spokeswoman Nanda Chitre would not comment on whether a lawsuit is being considered. “The Department of ­Justice is reviewing the ballot initiatives, and we have no additional comment at this time,” Chitre said.