TULSA COUNTY, Oklahoma - A summer-long investigation ends with a huge heroin bust in Tulsa.

Deputies arrested four people and said the drugs are connected to a Mexican cartel.

Investigators with the Tulsa County Sheriff's Office said they discovered almost three pounds of heroin and $25,000 in Martina Lopez-Mojica's apartment near 7th and Lewis.

Casey Roebuck with the Tulsa County Sheriff’s Office said they are searching every nook and cranny after finding drugs in a light fixture and even inside a box in the freezer.

"We are taking the screws out of vents. We're taking all the lights out of the ceiling because there could potentially be drugs hidden everywhere," said Roebuck.

Undercover agents with Homeland Security spent months buying heroin from Lopez-Mojica, leading up to her arrest Thursday.

The sheriff's office believes she's connected to a Mexican drug cartel and said she's been caught for drug trafficking almost 10 years ago, in Ohio.

But she made some connections in Tulsa, including Michael Darling. The sheriff's office said it Darling Thursday after finding marijuana and Xanax in his apartment.

For one nearby TU student, the drug bust is a reminder to stay vigilant.

"I think it's really important for college students to remember that even though we are part of this campus bubble, that's very protected by campus security, and we're seeing the same kind of people every single day, to remember that we really are in a city, even though we might feel a little bit removed," the student said.

The Oklahoma Bureau of Narcotics arrested a fourth person Thursday morning in connection to the case.

Wesley Smith's arrest report says agents found 20 grams of the drug and a firearm inside his residence. Agents said Smith was a buyer.