(CNN) The elections board in Florida's Miami-Dade County has collected a set of mysterious ballots in the Opa-locka mail facility after Democrats raised concern about the uncounted votes.

The uncounted ballots have emerged as one of many battles over the fiercely contested Florida elections that moved this weekend into a recount phase.

Suzy Trutie, a spokesperson for the county's supervisor of elections, told CNN there were 266 ballots in the shipment and that the votes will not be counted. Florida law requires all ballots sent by mail to arrive at the election facility by 7 p.m. on Election Day, and these ballots did not meet that standard, Trutie said.

The US Postal Service said in a statement on Friday that it was operating in "close coordination and partnerships with election officials at the local, county and state levels." But as of Sunday morning, it still did not confirm ballots had not been provided in time to local election officials.

By law, all ballots for federal races must be kept by an elections board for up to 22 months after the election, which means the ballots will not be destroyed and could theoretically be brought into a potential court case.

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