OKLAHOMA CITY -- A coalition of groups against a new immigration law that goes into effect on Thursday will rally at the state Capitol from noon to 2 p.m.

As of Nov. 1, illegal immigrants cannot get jobs or state benefits, and critics of the law call its implementation harsh. Pat Fennel, a leader with the Latino Community Development Agency in Oklahoma, said the law could have dire economic consequences for businesses that rely on immigrant labor.

The bill's author, Republican state lawmaker Randy Terrill, has said the people of Oklahoma support meaningful immigration reform and repeatedly stated he was confident it would hold up if challenged in the courts. An attempt to temporarily halt the law from taking effect failed on Wednesday.

However, law enforcement agencies have expressed concern that even more people could end up in already-crowded jail cells. Oklahoma County Sheriff John Whetsel said that while his deputies already checked residency status of those accused of most felonies, they will start checking the status of anybody accused of drinking and driving, too.

For those arrested who cannot prove their citizenship, they will end up in the county jail's immigration pod. Inmates will stay there until immigration and customs agents either pick them up for deportation or until they tell the sheriff's office to let them go.

The cells can hold about 100 people, and officials said that they're practically full. Whetsel said it could get even more crowded if federal agents are not prepared to handle a possible increase in arrests.

"We're hopeful that ICE will respond promptly, but we don't have any idea what kind of time frame will be required or will actually respond," he said.

However, the sheriff's office isn't sure just how many more arrests the immigration law will bring. He said his deputies won't be able to know whether somebody is an illegal immigrant until that person is booked.

"You're not going to be able to ascertain if they're legal or not just driving down the road. There's a process that you have to go through with ICE to make that determinations," Whetsel said.

The sheriff's office said it had no plans to send deputies to long training sessions because it would pull deputies off the streets. State lawmakers also provided no money for training.