Dykes told authorities that he had blankets and a heater in the bunker, and authorities have previously said the bunker -- built 4 feet underground -- has electricity.
Authorities did not say how they were communicating with Dykes.
Meanwhile, residents and business owners in Midland City put up blue, red and black ribbons in support of the boy and Poland. Blue and red are the local school colors, and black is in honor of the slain bus driver.
The U.S. Navy confirmed Monday that Dykes served in the military from 1964 to 1969.
Naval records list him as an aviation maintenance administrationman third-class who served with units based in California and Atsugi, Japan. The job entails clerical work related to aircraft and aircraft maintenance, according to the Navy's job description.
Neighbors and officials had described Dykes as a survivalist with "anti-government" views.
Even as the hostage situation continued Monday morning, plenty of police were on hand as schools in neighboring Ozark, Alabama, reopened for the first time since the incident began.
Dale County schools remained closed but were to reopen on Tuesday, the district said.
In Ozark, school officials decided to begin strictly enforcing a 15-foot safety zone around school buses required by state law. The law prohibits any unauthorized adults, including parents, from approaching within 15 feet of a school bus stop. If an unauthorized adult gets too close, bus drivers are supposed to close bus doors or drive away, if necessary, school officials said