By Susan Scutti, CNN

(CNN) -- More than 72,000 Americans died of drug overdoses in 2017, up nearly 7% from 2016, according to preliminary data from the US Centers for Disease Control and Prevention. The 2017 preliminary death count for all 50 states and the District of Columbia represents a twofold increase over a decade, the CDC says.

The authors of the report say the 2017 numbers may be an underestimate because states' investigations into some overdose deaths may not be complete.

Opioids, which include prescription painkillers along with heroin and other illegal synthetic opioid drugs, contributed 49,068 to the total number of overdose deaths, the report indicates. From 2002 to 2017, the CDC estimates a 4.1-fold increase in the total number of deaths due to all types of opioid drugs.

"The most striking patterns at the national level are the recent increases in the numbers of drug overdose deaths involving synthetic opioids (excluding methadone)," Lauren Rossen, co-author of the report and a statistician at the CDC's National Center for Health Statistics, wrote in an email.

Nearly 30,000 overdose deaths were related to fentanyl and other synthetic opioids in 2017, which is 22 times the number of deaths due to these drugs in 2002, the CDC finds.

When describing deaths involving specific drugs, "a single death might be included in more than one category," Rossen and lead author Farida B. Ahmad, of the Division of Vital Statistics at the CDC's National Center for Health Statistics, noted in the report. "For example, a death that involved both heroin and fentanyl would be included in both the number of drug overdose deaths involving heroin and the number of drug overdose deaths involving synthetic opioids other than methadone."

Breaking out the numbers in greater detail, they found that overdose deaths involving prescription pain relievers -- exclusive of synthetic opioids -- nearly doubled from 2002 to 2011, yet have remained relatively stable since.

The lowest number of overdose deaths due to cocaine, 4,312 in 2010, rose to a preliminary count of 14,556 in 2017, a 3.5-fold increase, the report also said.

Differences across the states include which specific drugs are involved in the deaths, Rossen noted.

"Prior studies have found that the numbers of drug overdose deaths involving synthetic opioids have increased more rapidly in states across the Midwest and Eastern US," she said. The new report shows this to be true, but the data are preliminary and so incomplete for some states.

"States in the Western part of the U.S. have not seen the same kind of increases in drug overdose deaths involving synthetic opioids," she added, noting that it is more common to see psychostimulants such as methamphetamine involved in drug overdose deaths in states like Oregon, Nevada and Washington.

Alex Ebied, a clinical assistant professor at the University of Florida College of Pharmacy, said that because opioid overdose deaths accounted for the majority -- nearly 68% -- of the preliminary total for 2017, the new report is "showcasing the opioid epidemic in the United States."

"It is important to note that this data encompasses both intentional and accidental overdoses," added Ebied, who was not involved in the CDC report.

Examples of accidental overdoses include children finding medications within arm's reach and chronic pain sufferers who have developed a tolerance for their medications and overdose when they try to control the pain from a severe episode, he said.

"While the opioid epidemic is a major concern, it is worth mentioning there are non-opioids overdoses representing 32.1%" of the total overdose deaths for 2017, Ebied said. "Any drug can be abused, but accessibility, cost and addictive properties are major factors."

He said that over-the-counter medications including acetaminophen, a non-opioid pain reliever, or loperamide, an anti-diarrheal, are also abused while ingestion of Tide detergent pods, K2 and "bath salts" are an emerging concern.

"The sharp increase in fentanyl and fentanyl analogs indicates there is abuse of access to this drug class," Ebied said, noting that fentanyl is 100 times more potent than morphine. "Although the Drug Enforcement Administration has a tight control of these controlled substances, accessibility continues to occur.

"A majority of abused prescription drugs were obtained from family and friends, often from the home medicine cabinet," Ebied said. He noted that there are increased efforts toward substance abuse awareness, including the Generation Rx Initiative, an educational program to increase public awareness of prescription medication abuse, and the National Prescription Drug Take Back Day, an initiative to dispose of unused drugs in a responsible way.

Other positive steps include increasing supply of naloxone, the opioid antidote, to first responders, while some states, including his own, are taking steps to limit opioid prescribing.