Williams' blood alcohol level was below the state limit of .08, but a sheriff's department spokesman said that Williams was seen speeding and weaving in traffic in a black Escalade around 2:30 a.m. ET.
Sheriff's deputies said his eyes were glassy and he smelled of alcohol.
Williams, 23, also submitted to a urine test, which can be requested if the officer suspects a driver is under the influence of something other than alcohol, the spokesman said.
Toxicology results could take four to six weeks.
A Buccaneers official told ESPN NFL Insider Adam Schefter that Williams was going 12 mph over the speed limit and was issued a speeding ticket.
Williams' blood alcohol levels were .065 and .061 in two different tests. He was released on $500 bond later Friday morning.
Authorities can conduct a DUI investigation if they see signs of impairment and make an arrest regardless of blood-alcohol or urine tests, sheriff's spokesman Larry McKinnon said.
"We are in the process of gathering all the facts," Buccaneers general manager Mark Dominik said in a statement released by the team. "Mike has been very cooperative."
Williams did not practice on Friday, but head coach Raheem Morris said he will travel with the team to San Francisco for Sunday's game against the 49ers.
"I'm very disappointed about the decision he made to be out late, and the worse decision he made to have a drink and drive," Morris said. He add that that after "gathering all the facts" he made the decision to allow Williams to travel with the team late Friday.
According to a team source, the Buccaneers plan to start Williams. The source said Morris met with the team's captains, including quarterback Josh Freeman and cornerback Ronde Barber, before making his decision.
The source said Williams also will have to address his team on the road trip.
"He will be disciplined. But it won't have to do with playing time," Morris added. "We'll deal with it internally, like we always do."
"I'm very pleased with his ability to be cooperative and not be disrespectful and make this thing even worse than it could be," Morris said.
A fourth-round draft pick out of Syracuse, Williams quickly emerged as Tampa Bay's top wide receiver from the start of the season. He has 40 catches for 627 yards and five touchdowns.
Morris said Williams had been making progress toward leaving questions about his character behind, adding that he hopes the young player learns from his arrest.
"It's disappointing because it was old news, and now you rehash and you've got to talk about it again," Morris said.
Pat Yasinskas covers the NFC South for ESPN.com. Information from The Associated Press was used in this report.