Hillary Clinton's campaign on Tuesday accused Barack Obama's camp of engaging in "outrageous" and "undemocratic" tactics during the voting in Texas, including locking her supporters out of caucuses.
The Obama camp denied the allegations as a "laughable" attempt to play down the state's caucuses, a political nominating exercise that has produced better results for their White House candidate in other states.
Clinton's Texas state director Ace Smith said there was a "really tremendously disturbing pattern" of vote irregularities in Texas, which conducted a statewide presidential primary Tuesday followed by caucuses.
"What is happening tonight is just truly an outrage," he told reporters.
The Clinton campaign accused the Obama operation of taking materials supposed to be available for both sides in the caucuses earlier in the day.
Clinton's aides also said in a hastily-convened conference call that in some locations in Texas her supporters had been locked out of caucuses by Obama backers, who had taken over the meetings.
The campaign's legal counsel Lyn Utrecht warned that some precincts in Texas had also called in results even before they were supposed to open.
"There are numerous locations where Obama supporters have taken over the caucuses and have locked out Clinton supporters who should have been allowed to come in."
She said all options were open for the campaign, including legal action, though no decisions had been taken.
Obama spokesman Bill Burton dismissed the allegations.
"This is a transparent and laughable attempt to divert attention from the caucus results which reward delegates every bit as meaningful as do primaries," he told AFP by email.
Texas has a unique electoral system which allows all eligible voters in the state to take part in day-long primary votes.
Once the polls closed, voters were then invited to take part in caucuses -- known here as convention -- to complete the selection process.
Roughly two-thirds of Texas's total 193 Democratic delegates are allocated according to the results of the primaries in the state's 31 electoral districts, and the remaining third come from the caucus process.
A spokesman for the Texas Democrat Party said it was doing everything it could to ensure problems were addressed immediately by its legal team at a center set up to respond to calls from concerned voters.
"Right now we're seeing record turnout in Texas and due to the fact that there are so many people participating, you are going to see some concerns and problems arising in the state," spokesman Hector Nieto told AFP.
"Our call center is informing the precinct captains what the rules and regulations are."
The party issued two memos citing problems at the polls, including out-of-state supporters trying to participate in the caucuses and the issuing of false credentials at caucuses.