NEW ORLEANS — Former New Orleans mayor Ray Nagin, best remembered for his impassioned pleas for help after the levees broke during Hurricane Katrina, was convicted Wednesday of accepting bribes in exchange for helping businessmen secure millions of dollars in city work, including after the storm.

The federal jury deliberated for about 6½ hours before finding Nagin guilty of 20 of 21 counts against him. He sat quietly at the defense table after the verdict was read and his wife, Seletha, was being consoled in the front row.

Nagin, 57, could be facing 20 years or more under federal sentencing guidelines. He will remain free on bond but was placed under home detention until sentencing, which was set for June 11.

Before the verdict, Nagin said outside the New Orleans courtroom: ‘‘I’ve been at peace with this for a long time. I’m good.’’

The trial lasted seven days, during which more than 30 witnesses testified, including some businessmen who had pleaded guilty to bribing the mayor in return for contracting work with the city.

‘I’ve been at peace with this for a long time. I’m good.’

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The Democrat, who left office in 2010 after eight years, was indicted in January 2013 on charges he accepted hundreds of thousands of dollars in bribes and truckloads of free granite for his family business in exchange for promoting the interests of local businessman Frank Fradella.

He also was charged with accepting thousands of dollars in payoffs from another businessman, Rodney Williams, for his help in securing city contracts.cn domain

Nagin testified that key witnesses lied and prosecutors misinterpreted evidence including e-mails, checks, and pages from his appointment calendar linking him to businessmen who said they bribed him.

As Nagin and defense attorney Robert Jenkins left the courthouse, walking with a throng of media, photographers, and video cameras, Nagin could be heard saying: ‘‘I maintain my innocence.’’

The defense repeatedly said prosecutors overstated Nagin’s authority to approve contracts. His lawyer said there is no proof money and material given to the granite business owned by Nagin and his sons was tied to city business.

The charges against Nagin included one overarching conspiracy count along with six counts of bribery, nine counts of wire fraud, one count of money laundering conspiracy, and four counts of filing false tax returns. He was acquitted of one of the bribery counts.

Each charge carries a sentence from 3 to 20 years, but how long he would serve was unclear and will depend on a presentence investigation and various sentencing guidelines.

Jenkins said Nagin’s testimony didn’t hurt the case and that they plan to appeal after sentencing.

Prosecutors say he took hundreds of thousands of dollars’ worth of bribes including money, free travel, and granite for Stone Age LLC, a family granite business.

They allege the corruption spanned the time before and after Hurricane Katrina struck in August 2005, plunging the city into chaos. cn domain

The conviction wasn’t a surprise to Rainelle Smith, 64, of New Orleans, who said she voted for Nagin.

‘‘I don’t believe he served the city as well as he should have,’’ she said. ‘‘He was supposed to come in and prevent the corruption the city was known for. We, in my family, thought of him as the ‘cleanup man.’ Instead he gets in office and he soiled it more.’’

The charges resulted from a City Hall corruption investigation that had resulted in several convictions or guilty pleas by former Nagin associates by the time the trial started Jan. 27.

Fradella and Williams, both awaiting sentencing for their roles in separate bribery schemes alleged in the case, each testified that they bribed Nagin.cn domain

Nagin’s former technology chief, Greg Meffert, who also is awaiting sentencing after a plea deal, told jurors he helped another businessman, Mark St. Pierre, bribe Nagin with lavish vacation trips. St. Pierre did not testify. He was convicted in the case in 2011.

Nagin said he did not know his vacation trips to Jamaica and Hawaii were paid for by St. Pierre. He also said he wasn’t told that a family trip to New York was paid for by a movie theater owner who, prosecutors said, received help with a city tax issue after Katrina wiped out the theater.

The prosecution’s case included several exchanges over charges of filing false tax forms.